"We've outlined what we think a deal has to look like on our end," Sanders said. She declined to elaborate on potential concerns with the proposal.

Lawmakers are scrambling to reach a deal on spending and immigration by Jan. 19, when government funding runs out and a government shutdown would occur. Democrats want a fix to protect DACA recipients, which Trump says he won't agree to unless the government funding bill also budgets for increased border security and his proposed border wall with Mexico.

Trump last year scrapped the Obama-era DACA program, which allows certain young immigrants brought illegally to the U.S. as children to live and work without fear of deportation.